PURPOSE: The purpose of this study was to examine the sensation changes in upper extremity and the quality of life for post-operative mastectomy patients. METHODS: This study used a descriptive study design. The participants were 132 women who had mastectomies after being diagnosed with breast cancer and were participating in breast cancer self-help groups. The sensation changes in the arm of the surgery site was measured by the arm symptoms which were subjective uncomfortable feelings of the affected arm, and the quality of life was measured by Medical Outcomes Study Short Form-36. Collected data were analyzed by ANOVA, t-test, chi2-test and multiple regression with SPSS WIN 12.0 program. RESULTS: Patients with stage IV breast cancer had severe changes in sensation of the arm. Participants with lymphedema had statistically significant changes in sensation compared to participants without lymphedema, but the quality of life was not different between the two groups. Pain by the SF 36 was statistically different between the two groups, with- and without-lymphedema. The factors in upper extremity's sensation changes which influence on quality of life were pain and heaviness. CONCLUSION: Nursing intervention for relieving pain and heaviness of the affected arm needs to be developed in order to improve QOL of the breast cancer survivors.